Burgessite is a rare cobalt arsenate mineral known primarily from its type locality in Ontario. It forms delicate, pale pink prismatic crystals that are visually similar to erythrite but distinct in crystal structure and composition.

Hardness

Mohs

Luster

Vitreous to adamantine

Streak

Colorless to pale pink

Transparency

Transparent

mineralrare

Burgessite

Hardness: ~3
Luster: Vitreous to adamantine
Streak: Colorless to pale pink
Transparency: Transparent

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Is this burgessite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch burgessite with a known reference. Burgessite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: colorless to pale pink.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to adamantine.
4
Match the color range
Compare against the expected color range: purplish pink.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic, rosette.

Often confused with

Burgessite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Erythrite

Mohs 1.5-2.5

How to tell apart: Streak differs, so Burgessite leaves colorless to pale pink, Erythrite leaves pale red to pink; luster reads vitreous to adamantine on Burgessite and subadamantine, pearly on cleavages on Erythrite.

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Often found alongside burgessite

Minerals reported to co-occur with burgessite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Co₂(H₂O)₄(AsO₃OH)₂·H₂O
Mohs hardness: ~3
Density: 2.93 g/cm³
Colors: Purplish pink
Streak: Colorless to pale pink
Luster: Vitreous to adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic, rosette
Cleavage: Good on {010}; fair on {001}
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral along fractures in the weathering zone of a polymetallic sulfarsenate deposit

Where rockhounds find burgessite

Classic worldwide localities

Keeley mine, South Lorraine Township, Timiskaming District, Ontario, Canada

Field-hunting tip

Where it forms: A secondary mineral along fractures in the weathering zone of a polymetallic sulfarsenate deposit. If you start seeing skutterudite, cobaltite, bismuth in float, you are in the right ground. Typical habit: prismatic, rosette. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify burgessite?+

Mohs hardness is ~3. Luster: vitreous to adamantine. The streak is colorless to pale pink. Common colors include purplish pink.

Where is burgessite found?+

Notable localities include Keeley mine, South Lorraine Township, Timiskaming District, Ontario, Canada.

Is burgessite safe to handle?+

Burgessite contains arsenic and cobalt and calls for real care. Contains arsenic and cobalt; wash hands thoroughly after handling and avoid ingestion or inhalation of dust.

What rocks look like burgessite?+

Burgessite is most often confused with Erythrite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with burgessite?+

Burgessite commonly co-occurs with Skutterudite, Cobaltite, Bismuth, Arsenolite, Bismuthoferrite, Erythrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does burgessite form in?+

Where it forms: A secondary mineral along fractures in the weathering zone of a polymetallic sulfarsenate deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is burgessite used for?+

Burgessite is used in collector.

Find burgessite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.